IEC 61811-1:2015 applies to electromechanical telecom elementary relays. Relays according to this standard are provided for the operation in telecommunication applications. However, as electromechanical elementary relays, they are also suitable for particular industrial and other applications. This standard selects from IEC 61810 series and other sources the appropriate methods of test to be used in detail specifications derived from this specification, and contains basic test schedules to be used in the preparation of such specifications in accordance with this standard. Detailed test schedules are contained in the detail specifications. This second edition of IEC 61811-1 cancels and replaces IEC 61811-1 published in 1999, IEC 61811-10 published in 2002, IEC 61811-11 published in 2002, IEC 61811-50 published in 2002, IEC 61811-51 published in 2002, IEC 61811-52 published in 2002, IEC 61811-53 published in 2002, IEC 61811-54 published in 2002, IEC 61811-55 published in 2002, and constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous editions: a) to get one document for telecom relays; b) update all relevant references.